At least 24 States and the District of Columbia have either implemented drug testing or developed guidelines for drug testing programs. Authority for these programs has come from a variety of sources: statutes, collective bargaining agreements, executive orders, attorney general's opinions, State personnel rules, and departmental rules or procedures. Few States employ random testing of all employees. Instead, most test on the basis of probable cause or reasonable suspicion. States with collective bargaining agreements with their employees include drug testing proposals in the negotiation process. Legal and constitutional issues are discussed in detail since drug testing impacts the guarantees of the 4th, 5th, and 14th amendments to the U.S. Constitution. Procedures to ensure drug test accuracy are also discussed. 14 footnotes.